Kurzfassung

The work performed in 2013 by the X-TRAS (Expertise Raumtransportsysteme) group of DLR on the critical analysis of the Ariane 6 PPH architecture is presented in this report. A first design iteration loop has been performed, based on the Ariane 6 configuration of the Concept Selection Key Point (triangular positioning of the three P135 of the first stage).
A preliminary model of the launcher with three P135 solid rocket motors (SRM) in the first stage, one identical P135 solid rocket motor in the second stage and a H30 cryogenic stage powered by Vinci was established. Subsequently, specific areas were analysed in more detail. Computational fluid dynamic (CFD) calculations have been performed to determine the aerodynamic characteristics of the launcher and to validate the aerodynamic database obtained with engineering method and, used for trajectory optimisation. Numerous parameters of the P135 solid rocket motors (amongst others performance, internal flow, pressure and thrust oscillations, and heat transfer) have been analysed and a preliminary design of the casing, the nozzle, the igniter and the grain have been performed. Using finite element methods, the main structure of the launch vehicle including the solid rocket motor casing, the inter-stages and the upper stage have been sized. In addition the stiffness was adapted to guarantee that the lower natural frequencies of the launch vehicle are high enough to ensure the launcher’s stability and controllability in flight. The propellant feed system of the upper stage has been pre-sized for the reference GTO-DDO (direct de-orbiting) mission. Sloshing in the tanks has been calculated with CFD methods. A preliminary selection of the subsystems was performed based on existing launch vehicles.
The controllability and stability of the launch vehicle has been verified under the influence of wind gusts for the configuration of Ariane 6 LS-PRR, linear positioning of the three P135 of the first stage (October 2013). The case of thrust asymmetry, due to different burning rate of the solid rocket motors of the first stage, was also considered.
Preliminary analyses of the de-orbitation and launcher visibility from ground stations during its ascent were also performed.
Based on all these results a new mass breakdown and flight sequence was established and the optimal GTO trajectory determined.
An assessment of the development cost, production cost and launch service cost has been performed with the help of a parametric method and considering different scenarios.